The present invention relates to a recording method of a magneto-optical recording for use in high density recording in a magneto-optical recording in which information can be recorded, reproduced or erased by a laser light and an externally applied magnetic field. In addition, the present invention relates to a recording method for use in establishing a compatibility between media.
Heretofore, three kinds of disks, i.e., a read only optical disk, a write once optical disk and an erasable optical disk have been commercially available on the market as the optical recording disk. Particularly, a magneto-optical recording disk is widely used as an erasable memory, a document file or an image file.
Recently, many research institutes had advanced research and development of the disks in order to improve disk performance. One of the improvements of disk performance is to improve a recording density. A recording system that can improve a recording density employs a mark length recording format, a zone CAV (constant angular velocity) format or the like, Further, other researches that are independent of the recording system are advanced in order to improve a recording density by reducing a track pitch and a bit pitch and by using a laser light source of a short wavelength, etc.
A recording capacity of a current 5.25-inch single-sided disk is 320 MB. The research and development are now advanced in order to achieve a recording density of at least three times the above-mentioned recording capacity as a target recording capacity.
The magneto-optical recording is fundamentally a thermo-magnetic recording so that, in order to increase a recording density, the recording must be effected while a micro-recording magnetic domain is stable and without an interference between recording magnetic domains. Particularly, when the mark length recording format is used, an edge shift must be suppressed.
Further, since the optical disk is a compatible medium, better system conditions are to maintain a compatibility between the media or a compatibility between the apparatus. As described above, the magneto-optical disk are individually different in recording conditions, such as optimum recording power, erasing power or the like. Therefore, in order to keep compatibility between the media and between the apparatus, there have heretofore been proposed the following methods. That is, points at which recording conditions and so on are recorded on the control track of the disk are defined on the ISO standard in advance to thereby maintain a compatibility between the disks. Also, a standard disk for calibrating recording power is prepared in advance for an apparatus used, and a disk whose recording power is determined by the relative comparison of the disk with the standard disk is manufactured.
On the other hand, when data is recorded by using the mark length recording system as a data recording system, a shift amount of a mark edge is corrected under the control of signal. In particular, in the case of the heat flow generated within the recording medium and the magneto-optical recording, the control of the magnetic characteristic exerts a large influence upon the shift amount of the mark edge position, as earlier noted. In the mark length recording, information is recorded on the basis of the length of the mark formed so that the shift amount of the mark edge position is directly related to the high density recording and the high accuracy recording.
In order to solve the aforesaid problems, there is known the following examples according to the prior art.
JP-A-3-22223 realizes a control technique in which a magnetic domain shape is controlled with high accuracy by controlling the shape of the recording waveform. To be more concrete, a code string of the recording mark is converted into pulses and a series of pulse string corresponding to the length of the recording code string is formed. Then, the length and amplitude of the pulse string are controlled in response to the length of the opposite phase of the recording code string. Thereafter, the pulse string is separated into three portions and data is recorded by changing the pulse width of each pulse.
In the above-mentioned technique according to the prior art, adequate accuracy required when the shape of the recording magnetic domain is controlled in order to realize a recording capacity of high density is not always obtained. Consequently, an error of the magnetic domain shape is observed as the edge shift, which causes an error frequently. This is a large hindrance encountered when the ultra-high density recording is realized by using the mark length recording system.
Further, when an ambient temperature is fluctuated or an interference occurs between data patterns, then a desired magnetic domain shape cannot be obtained, which causes the edge shift and the error. Therefore, it is impossible for the above-mentioned conventional technique to obtain reliability.
JP-A-4-265522 describes a technique in which information is recorded without being affected by the mark edge position shift and the information thus recorded is reproduced. To this end, a constant pattern is recorded on a disk as an initial operation and the edge position shift is detected by reproducing the recorded constant pattern. Then, an information reproduced signal is shifted on the basis of the detected shift amount. In particular, JP-A-4-265522 describes a technique proposed on the recording medium side and on the apparatus side so as to realize a compatibility. However, when the apparatus treats a recording medium having an unspecified recording condition, the apparatus must allow an error signal of a certain extent occurred when data is recorded or reproduced. Accordingly, when the recording density of the recording medium is increased, a tolerance of the above-mentioned error signal is reduced so that the high density recording cannot be substantially achieved by the recording medium having a compatibility. In particular, when data is recorded by using the mark length recording system while the track pitch is reduced or the bit pitch is reduced, an influence of a thermal interference between the pits is large and a compatibility cannot be maintained. The reason for this is as follows. That is, a heat characteristic of the disk is different so that controllability, in particular, control accuracy of the mark to be formed is different.
An object of the present invention is to provide a recording control method of a magneto-optical recording in which disadvantages, such as fluctuation of ambient temperature and interference between patterns can be eliminated and in which a very small magnetic domain suitable for effecting a mark edge recording can be formed stably.
Another object of the present invention is to provide a recording control method of a magneto-optical recording in which information can be recorded or reproduced with high density and with high accuracy.
A further object of the present invention is to provide a recording control method of a magneto-optical recording in which a recording magnetic domain of desired width and length can be obtained.